In view of the fact that the yarn is supplied to the storage body of a yarn feeder from one side, is deposited in turns on said storage body and is then, in most cases overhead and in a circulatory movement, removed on the other side, the storage body must be supported rotatably on the drive shaft of a yarn winding member and it must be prevented in a contactless manner from rotating together therewith. An eccentric weight provided on the storage body and acting through the force of gravity can, for example, be used as a means for preventing the storage body from rotating. In practice, however, the measure of arranging mutually oriented holding magnets in the housing and in the storage body has become generally accepted, said holding magnets guaranteeing, thanks to magnetic forces, that the storage body is prevented from rotating. The holding magnets have, however, the disadvantage that the smallest force preventing the storage body from rotating will occur when the holding magnets are fully aligned with each other, whereas said force will increase progressively in response to a relative rotational displacement of the storage body. Within the large speed range of the drive shaft, resonance phenomena will occur, and these resonance phenomena will result in rotary oscillation movements of the storage body about the axis of the shaft. These oscillation movements are extremely disadvantageous when the machine is in operation, especially if the amplitude at the external circumference touched by the turns of the yarn increases to 1.5 mm or to an even higher value.
There is the risk that the turns will no longer be transported properly to the unwinding side, that sensors directed onto the turns will not respond in an adequate manner and that heavy wear and damage will result from the forces of gravity. In the case of socalled measuring weft feeders comprising at least one stopping device which acts on the storage body by means of a stopping element at certain intervals for blocking then drawing off of the yarn, the rotary oscillation movements will result in detrimental forces acting on the stopping element. Moreover, the response behaviour of a yarn sensor, which is integrated in the stopping device in most cases, will be impaired by said rotary oscillation movements. Finally, in the case of yarn feeders operating according to the socalled yarn separation principle, the mass of the storage body is comparatively big because of the components in the storage body which are required for the yarn separation process, and this will tend to generate large amplitudes of the rotary oscillation movements and, possibly, detrimental forces of gravity. Since a mechanical access to the storage body from the side of the stationary housing for the purpose of supporting the storage body against these oscillation movements is impossible due to the movements of the yarn, it has, up to now, been unavoidable to put up with said oscillation movements.
It is true that, in the case of a measuring weft feeder provided with a wobbling ring which is arranged behind the yarn supply and which is used as an advance element of the storage body, it is known to use the wobbling movement for touching the wobbling ring periodically from outside by means of a pressure bow so as to interfere with the generation of rotary oscillation movements of the storage body. This principle is, however, bound to the use of a wobbling ring.
It is also known to provide the storage body with an extremely small and light structural design and to arrange a very large number of holding magnets also within the storage body for suppressing the rotary oscillations by very high magnetic forces. Extremely small storage bodies will, however, result in problems with respect to the course of the yarn. Moreover, the holding magnets are very expensive.
It is the object of the present invention to provide a yarn feeder of the type mentioned at the beginning in the case of which rotary oscillation movements of the storage body are prevented or at least reduced to a tolerable extent.
In accordance with the present invention, this object is achieved by providing the storage body with an oscillating body which is connected thereto by a damping connection such that the oscillating body is movable relative to the storage body and acts as a damping mass.
In view of the fact that the oscillating body is arranged such that it is movable relative to the storage body and is connected to said storage body via a frictional connection, a rotary oscillation movement of said storage body will excite a movement of said oscillating body, said movement occurring, however, as a phase-displaced movement. Due to the phase-displaced movement of the oscillating body and the frictional connection with the storage body, a consumption of energy will occur between the storage body and the oscillating body, and this consumption of energy will result in an effective damping of the rotary oscillations of the storage body at least down to a tolerable extent, i.e. an externally detectable amplitude of approx. 0.5 mm or less. The oscillating body will damp the rotary oscillations of the storage body although, just as the storage body, it cannot be acted upon mechanically from outside in a direct manner, and although it impairs neither yarn deposition, nor yarn storage nor the unwinding of the yarn.
A sufficient rotary positioning of the storage body can be achieved by a small number of and by comparatively weak holding magnets which constitute only a subordinate factor in the total costs of the yarn feeder. The basic concept of the yarn feeder remains practically unchanged in spite of the integrated damping measures.
In an expedient embodiment, the oscillating body is a solid material with a high specific gravity, such as metal, and is secured coaxially on the storage body so as to permit relative movement of the oscillating body to a limited extent. When a rotary oscillation builds up at the storage body, a phase-displaced rotary oscillation of the oscillating body will occur and result in the desired damping.
Thanks to the high specific gravity of the oscillating body, said oscillating body requires only little space for causing effective damping, and, taking into account the limited space conditions within a yarn feeder, this is extremely important. The centered arrangement of the oscillating body avoids undesirable eccentric forces. The fact that the oscillating body is secured in position guarantees that it cannot separate from the storage body.
In an additional expedient embodiment, the oscillating body is a one-piece component disposed on the end face of the storage body facing a winding member in the interspace therebetween. At least one magnet is secured to the end face in an oscillating body recess. The oscillating body utilizes in an advantageous manner the small interspace, which is available anyhow, for accommodating the holding magnet on the storage body. Hence, no fundamental change in the structural concept of yarn feeders which have already proved to be useful is necessary. Furthermore, yarn feeders which have already been in operation can be converted subsequently by inserting an adequately adapted oscillating body. Especially for yarn feeders having no wobbling ring as an advance element, but having other types of advancing drives or working perhaps even with yarn separation, the oscillating body is a simple, economy-priced and optimum solution of the rotary oscillation problem.
In the case of the embodiment wherein a soft-iron carrier is used to position a holding magnet, the oscillating body is placed in the interspace which is necessary due to the arrangement of the holding magnet, said holding magnet being positioned within a recess of the oscillating body. Additionally, a rotary coupling prevents the oscillating body from rotating on the storage body. The rotary coupling operating with a certain amount of rotational play guarantees that the oscillating body will not strike the holding magnet and be deprived of its damping function. A feature which is advantageous from the structural point of view is the use of the soft-iron carrier for securing the oscillating body in position, the provision of said soft-iron carrier being necessary for fixing the holding magnet anyhow.
In the case of the embodiment wherein the rotary coupling includes a projectionlike engagement member which cooperates with a recess in the oscillating body, the rotary coupling forms an elastic rotation-prevention means for the oscillating body for suppressing impactlike contact between the storage body and the oscillating body on the one hand and for guaranteeing the rotational play of the oscillating body, which is necessary for damping the rotary oscillations, on the other. The engagement member, which may be constructed as a bending spring arm, serves so to speak as an emergency stop in case the oscillating body should become excessively displaced from the position constituting the desired oscillation damping position. As far as oscillation damping is concerned, the rotary coupling does not fulfil any direct function.
A simple embodiment, in the case of which an effective frictional connection is provided between the oscillating body and the storage body, the oscillating body includes a central bushing slidably fitted on a bearing by which the storage body is supported on the shaft. It is, however, just as well imaginable to provide between the oscillating body and the storage body additional areas of contact. Finally, the sliding fit on the bearing reception means of the storage body also guarantees a desirable centering of the oscillating body relative to the axis of the drive shaft.
In the case of the embodiment wherein the oscillating body contacts the storage body, energy consumption in the oscillation damping process is achieved by mechanical sliding friction. It would, however, be just as well imaginable to use rolling friction or other types of friction so as to achieve energy consumption in these areas.
In view of the fact that the friction occurring in the oscillation damping process is causally responsible for oscillation damping, providing a friction lining, which is adjustable and/or replaceable in the area of mutual contact between the oscillating body and the storage body offers the possibility of guaranteeing a desired and/or uniform friction from the very beginning. If necessary, the friction conditions can also be changed subsequently for adjusting the damping effect so to speak purposefully to the yarn feeder speed range causing the strongest rotary oscillations.
A particularly effective damping of the rotary oscillations of the storage body is obtained by making the damping mass proximate the mass of the storage body plus any insert members mounted thereon, even in cases in which said storage body is equipped with additional components required for yarn separation. However, in view of the fact that the damping effect achieved also depends on structural features, viz. on the radius of inertia of the oscillating body, on the distribution of weights within the storage body and/or within the oscillating body, and the like, it may definitely also be expedient to choose the mass of the oscillating body smaller or larger than the mass of the storage body or to distribute the oscillating body to several separate masses.
A very good and fast-responding damping effect is achieved wherein the damping mass corresponds to the storage body mass and preferably is a plastic, if the structural conditions permit the provision of this feature.
The oscillating body need not necessarily be arranged on one axial side of the storage body or the other, but it can just as well be positioned in the interior of the storage body. Also mixed forms are imaginable, in the case of which individual parts of the oscillating body are arranged such that they are distributed in the circumferential direction and also in the axial direction.
An additional advantageous embodiment is disclosed wherein the oscillating body is connected to the storage body by a plastically deformable anti-slip and/or bonding layer having a high internal friction. The anti-slip and/or bonding layer guarantees positioning and centering of the oscillating body on the storage body. Due to the internal friction, said anti-slip layer also has the effect that energy will be consumed during the oscillation damping process. It will be expedient when the anti-slip layer is as inelastic as possible so as to eliminate a spring effect to the best possible degree.
An additional advantageous alternative is disclosed wherein the oscillating body is arranged in a cavity within the storage body. In the case of this alternative, the oscillating body consists of a filling of heavy grains or balls or objects having some other shape, which, when moving relative to the storage body, can consume energy due to friction.
Alternatively, the oscillating body can also consist of a plurality of inserted weights placed in cavities of the storage body or in a separate carrier body for these inserted weights. Said inserted weights can be accommodated in the cavities such that they are freely movable therein.
An additional alternative is disclosed wherein the oscillating body is pendulumlike. The pendulumlike oscillating body consumes energy in its swingtype suspension and, possibly, in frictional contact with the storage body.
In accordance with an additional embodiment where a displaceable or elastically deformable material having a high internal friction is placed within a cavity, the material may be a liquid, paste-like substance, a granulate or a powder. The displaceable or elastically deformable material can be provided as an additional measure improving the damping effect, said displaceable or elastically deformable material opposing an energy-consuming resistance to the relative movement of the oscillating body.
If this material is e.g. a liquid or a pastelike substance, the damping effect can be improved still further by means of the throttle passage, which causes an additional consumption of energy when the material in question passes therethrough.